Modeling and dating glacier fluctuations and their relation to Pacific Ocean climate

Abstract:

This thesis presents the results of an investigation into the interactions between the present-day South Cascade Glacier and the former Mauna Kea ice cap at short (annual to centennial) and long (millennial and multimillennial) time scales. To quantify the response of South Cascade Glacier to atmospheric conditions, a surface energy balance model has been developed. This model has been applied to annual simulations of the mass balance of South Cascade Glacier and is shown to faithfully simulate ablation on all time scales from daily to seasonal. An investigation into the sensitivity of this model to uncertainties in the physical parameters and input data is conducted and provides a comprehensive indication of the uncertainty associated with surface energy balance model estimates of mass balance. These uncertainties are of the order of 10% of the annual mass flux of the glacier. The model is then used in conjunction with a regional model downscaling of climate data and a high resolution (0.5°) gridded observational data set to compute the long-term mass balance history of South Cascade Glacier. Our simulations show that the greatest rate of volume loss in the history of the glacier was in the late 1930s through the mid 1940s. However, present day mass loss is equivalent despite the more climatologically favorable position of the glacier today. Simulated mass balance is compared with Pacific climate indexes and show that the glacier’s relationship to oceanic conditions peaked in the middle part of the 20th century and currently shows a
sharp decline. Finally, we present an investigation of the deglacial chronology of Mauna Kea. Our results establish the age of the local last glacial maximum at an age of 22.1 ± 2.1 kyr BP and complete deglaciation was underway by 14.7 ± 1.4 kyr BP. We present strong evidence that retreat after the LGM was followed by a readvance at 16.1 to 16.8 kyr BP. The timing of this readvance is comparable to that of Heinrich event 1 in the North Atlantic. The connection between the North Atlantic and Hawaii climate is discussed in terms of atmospheric modeling results and proxy evidence.